Automotive vehicles have been produced with computer-controlled brake systems that modulate brake force during stops to provide anti-lock brake (ABS) control and/or that modulate brake force during vehicle acceleration to provide positive acceleration traction control (TCS). Recently, more comprehensive computer-based vehicle control systems have been developed that provide additional chassis control under braking or positive acceleration conditions. Such systems are described, e.g., in U.S. Pat. Nos. 5,720,533 and 5,746,486, both entitled "Brake Control System" and assigned to the assignee of this invention. These systems seek to control, among other parameters, the yaw rate of the vehicle.
The computer in the chassis control systems described in these patents uses signals from a variety of sensors such as wheel speed sensors, steering wheel angle sensors, brake switch sensor, master brake cylinder pressure sensor, yaw rate sensor, lateral accelerometer and the like. For further development of such control systems, it is desirable and/or necessary to provide algorithms or computer-controlled processes for eliminating some of such sensors or for detecting faults in their operation.
For example, a process has been developed that permits vehicle control based on an estimated yaw rate rather than the output of a yaw rate sensor or lateral accelerometer. This practice is described in U.S. Ser. No. 09/080,372, filed May 18, 1998, titled "Vehicle Yaw Control Based on Yaw Rate Estimate" and assigned to the assignee of this invention.
The vehicle yaw rate can be computed as a function of the measured speeds of the non-driven wheels of the vehicle and the distance between the center of the wheel treads (i.e., the track). However, the estimate may fail to equal the actual vehicle yaw in a vehicle with a relatively high center of gravity due to the relatively high body roll of the vehicle. When a vehicle with large body roll and high center of gravity is driven under high lateral acceleration, the outside tire is compressed and the radius of the inside tire is increased. Therefore, the estimated yaw rate is higher than the actual yaw rate of the vehicle. It is desired to compensate for the yaw rate estimation, without a yaw sensor or lateral acceleration sensor, and control vehicle yaw rate even during conditions that have previously degraded the yaw rate estimation such as in vehicles with large body roll and high center of gravity.